Effects of type 1 diabetes on reflexive cardiovascular responses to intermittent muscle contraction.

Studies have shown that early-stage type 1 diabetes mellitus (T1DM) leads to an exaggerated reflex pressor response to both static muscle contraction and tendon stretch. However, whether similar responses are present during dynamic exercise (i.e., intermittent contraction) is not known. Therefore, the purpose of this study was to determine whether T1DM leads to an exaggerated reflex pressor response to intermittent muscle contraction. We measured the exercise pressor reflex in unanesthetized, decerebrated T1DM (50 mg/kg streptozotocin; STZ) and healthy control (CTL) Sprague-Dawley rats by intermittently contracting the hindlimb muscles for 30 s while measuring mean arterial pressure (MAP), renal sympathetic nerve activity (RSNA), and heart rate (HR). Intermittently contracting the hindlimb muscles evoked exaggerated mean RSNA (STZ: Δ109 ± 21%, n = 4 rats; CTL: Δ61 ± 8%, n = 5 rats, P < 0.05), peak MAP (STZ: Δ32 ± 2 mmHg, n = 9 rats; CTL: Δ12 ± 2 mmHg, n = 6 rats, P < 0.05), blood pressure index (STZ: Δ625 ± 60 mmHg/s, n = 9 rats; CTL: Δ241 ± 46 mmHg/s, n = 6 rats, P < 0.05), and HR (STZ: Δ24 ± 3 beats/min, n = 9 rats; CTL: Δ9 ± 3 beats/min, n = 6 rats, P < 0.05) responses to similar developed tensions (P > 0.05) in T1DM compared with CTL rats. T1DM rats also exhibited exaggerated early-onset sympathetic (onset: 1 s) and pressor (onset: 5 s) responses. These data show that early-stage T1DM leads to an exaggerated pressor reflex evoked by intermittent muscle contraction. The early onset and greater blood pressure index suggest that cardiovascular strain during dynamic exercise may be significantly higher in individuals with T1DM.NEW & NOTEWORTHY This is the first study to provide evidence that early-stage type 1 diabetes mellitus (T1DM) leads to an exaggerated exercise pressor reflex evoked by intermittent muscle contraction, resulting in substantially higher cardiovascular strain. These findings are significant as they indicate that interventions targeting the exercise pressor reflex may work to alleviate the increased cardiovascular strain and overall burden during exercise in T1DM.